Quantitative thin-layer chromatographic method for the determination of procainamide and its major metabolite in plasma

A sensitive and accurate spectrodensitometric method was developed for the determination of procainamide and its major metabolite, N-acetylprocainamide, in plasma. The method involves extraction into organic solvent at alkaline pH, separation by thin-layer chromatography and direct measurement of the adsorbance of the compounds on the plate at 275 nm. Quantities as low as 10 ng could be measured and a linear relationship was obtained between peak areas and amounts of the compounds in the spots from 10 to 200 ng. The recovery of both drugs from plasma was from 95.4 to 104.8%. The method is sensitive and specific, and procainamide was well separated from N-acetylprocainamide at all investigated concentrations. The method is recommended for clinical assays and pharmacokinetics studies.